Wrack mostly consists of the kelp that washes onto beaches from the ocean. Wrack is an essential part of the ecology of the shoreline, providing food and habitat for everything from insects to birds.
A figure showing the averaage density of two important sandy beach-dwelling invertebrates (shown in red and blue) from eight surveyed beaches on Santa Rosa Island from 1994 to 2015. Figure credit: Channel Islands National Park.

A figure showing the averaage density of two important sandy beach-dwelling invertebrates (shown in red and blue) from eight surveyed beaches on Santa Rosa Island from 1994 to 2015. Figure credit: Channel Islands National Park.

Click for Details Mean density of two important members of the upper beach macrofaunal community — California beach hopper (Megalorchestia californiana) (red) and (Alloniscus perconvexus) (blue ) — from surveys of eight beaches on Santa Rosa Island from 1994 to 2015. Curved lines represent statistically smoothed means. For more information, consult Figure App.F.13.8 in the CINMS 2016 Condition Report.